Application Of Nitrification Inhibitors Research Articles

Non-targeted effects of nitrification inhibitors on soil free-living nitrogen fixation modified with weed management

Biological nitrogen fixation and nitrification inhibitor applications contribute to improving soil nitrogen (N) availability, however, free-living N fixation affected by nitrification inhibitors has not been effectively evaluated in soils under different weed management methods. In this study, the effects of the nitrification inhibitors dicyandiamide (DCD) and 3, 4-dimethylpyrazole phosphate (DMPP) on the nitrogenase, nifH gene，and diazotrophic communities in soils under different weed management methods (AMB, weeds growth without mowing or glyphosate spraying; GS, glyphosate spraying; MSG, mowing and removing weeds and glyphosate spraying; and WM, mowing aboveground weeds) were investigated. Compared to the control counterparts, the DCD application decreased soil nitrogenase activity and nifH gene abundance by 4.5 % and 37.9 %, respectively, under the GS management method, and the DMPP application reduced soil nitrogenase activity by 20.4 % and reduced the nifH gene abundance by 83.4 % under the MSG management method. The application of nitrification inhibitors significantly elevated soil NH4+-N contents but decreased NO3−-N contents, which had adverse impacts on soil nifH gene abundance and nitrogenase activity. The nifH gene abundances were also negatively impacted by dissolved organic N and Geobacter but were positively affected by available phosphorus and diazotrophic community structures. Nitrification inhibitors significantly inhibited Methylocella but stimulated Rhizobiales and affected soil diazotrophic communities. The nitrification inhibitors DCD and DMPP significantly altered soil diazotrophic community structures, but weed management outweighed nitrification inhibitors in reshaping soil diazotrophic community structures. The non-targeted effects of the nitrification inhibitors DMPP and DCD on soil free-living N fixation were substantially influenced by the weed management methods.

Reducing methane and nitrous oxide production in different soil types through utilizing Turmeric Rhizome (Curcuma domestica Val)

Indonesia is rich in flora diversity which is used to support agricultural development. One of the useful plants in agricultural cultivation is turmeric rhizome. Turmeric rhizome (Curcuma domestica Val) is a natural ingredient that can function as an inhibitor of the production of methane and nitrous oxide in the soil. A laboratory experiment aimed to determine the potential of turmeric rhizome on the production rate of CH4 and N2O in different soil types. The experiment used a completely randomized factorial design with 3 replications, the treatment was soil type factor and nitrification inhibitor factor. The rate of GHG production (methane and nitrous oxide) in the application of nitrification inhibitors (NI), both natural (turmeric rhizome) and commercial (DCD) was lower than without the application of NI on Inceptisols, Vertisols, and Alfisols. Turmeric rhizome natural ingredients provide promising prospects that are cheap and easy to obtain as an inhibitor of the rate of CH4 and N2O production for paddy fields.

Ammonia emission and nitrogen use efficiency with application of nitrification inhibitor and plant growth regulator in a calcareous soil (Karaj, Iran)

Ammonia volatilization (AV) is one of the main potential pathways of nitrogen (N) loss and re-deposited ammonia acts as an indirect source of N2O. The question arises how environmentally friendly inputs such as nitrification inhibitors (NI) and plant growth regulators (PGR) can affect AV in calcareous soils, while increasing nitrogen use efficiency (NUE) and crop yield. To answer this question, the effects of applying urea in combination with nitrapyrin (NP) as a NI and gibberellic acid (GA3) as a PGR on daily AV, winter wheat yield and NUE were evaluated. The treatments included a control treatment, urea and urea+NP + GA3 with five replications. Urea and urea coated with NP were applied in three equal split applications, and GA3 was foliar sprayed once. By using 15N-labeled urea and setting up three 15N microplots inside each plot, the nitrogen in the plant derived from fertilizer (Ndff) and the fate of N fertilizer were directly investigated. Ammonia emission factors and estimated values of indirect N2O-N produced from AV in urea and urea+NP + GA3 were 27% and 33%, and 0.38 and 0.45 kg N ha−1, respectively. The grain yield and 1000-grain weight in urea+NP + GA3 treatment were significantly increased by 15% and 13%, respectively, compared to urea. However, urea coated with NP increased AV and decreased Ndff by about 22% and 15%, respectively. The increase in AV caused by the addition of NP was relatively lower than amounts reported in previous studies. This could be due to the split application of N fertilizer on dry soil, the immediate incorporation and the ammonium fixation capacity of illite and vermiculite clay minerals presence in this soil and the reduction of readily available NH4+. The N difference method displayed 21% increase in NUE when urea was applied with NP and GA3 but tracking 15N showed that the combination of urea+NP + GA3 reduced NUE by about 8%. This suggests that NP may not be a viable option for increasing NUE in calcareous soils due to its ability to increase AV. Further research is needed to study the combination of other NIs with GA3 and investigate their effect on AV to simultaneously improve yield and NUE.

Adding nitrification inhibitors to N fertilisers induces rhizosphere acidification and enhances P acquisition: A meta-analysis

Ammonium (NH4+) absorption by crops enhances inorganic phosphate (Pi) acquisition efficiency mediated by rhizosphere acidification. The application of nitrification inhibitors (NIs) prolong NH4+ retention in soil by inhibiting ammonia oxidation and facilitating ammonium uptake by crops which may promote crop P utilisation. However, the efficacy of NIs on enhanced P-utilisation efficiency has not been comprehensively evaluated, and the mechanism underlying these effects remains unclear. Here, a meta-analysis of 92 peer-reviewed articles (1217 paired observations) was conducted to investigate soil pH and crop P absorption changes under NIs amendment, and boosted regression tree model was adopted to identify the primary factor regulating enhanced P-efficiency. The results showed that the addition of NIs reduced the rhizosphere soil pH by 12.37% and increased bulk soil pH by 2.38%, increased plant N and P uptake by 16.09% and 8.49%, respectively, and shoot N and P concentrations by 4.38% and 6.73%, respectively. NIs significantly decreased the crop N/P ratio and alleviated P limitation for crop production. Fertiliser (N and P) application method, NI product type, and soil properties (soil organic carbon, available P, total N content and soil texture) are major factors affecting crop P uptake. Using dicyandiamide (DCD) or 3,4-dimethylpyrazole phosphate (DMPP) as NIs combined with the application of ammonium-based fertiliser, adoption of subsurface or one-time N application, or application of these fertilisers to coarse-textured soils could significantly decrease rhizosphere soil pH while increasing crop P uptake. This study quantitatively demonstrated the positive impact of NIs on crop P acquisition using a meta-analysis approach, enhanced the knowledge on the incidental efficacy of N stabilisers and provide a strategy for the sustainable management of N and P in agriculture.

The influences of graphene oxide and nitrification inhibitor on vegetable growths and soil and endophytic bacterial communities: Double-edge sword effects and nitrate risk controls

Crop yield and quality are substantial indicators of evaluating agricultural nitrogen management practices, and the nitrate (NO3−-N) is one of the predominant factors affecting crop quality. The NO3−-N accumulation in vegetable crop affects plant growth and quality and human health. Therefore, it is necessary to stimulate vegetable yield but eliminate excessive NO3−-N in soils and plants with feasible management strategies. Graphene oxide (GO) is a novel carbon nanomaterial that has attracted great attention, but rare research has been conducted to quantify the effects of GO on plant NO3−-N accumulation and microbial communities. This study explored effects of the GO and nitrification inhibitors, dicyandiamide (DCD) and 3, 4-dimethylpyrazole phosphate (DMPP), on vegetable yields and NO3−-N contents and bacterial communities in soil-cabbage (Brassica rapa subsp. Chinensis) system. The soil NO3−-N content was significantly reduced with the single GO application. The cabbage NO3−-N content was increased by 60.4 % while the cabbage yield was significantly enhanced by 101.9 % with the single GO application. Meanwhile, the Invsimpson index of soil bacterial community and the ACE and Chao1 richness estimators of endophytic bacterial community were significantly decreased by the GO application. Cabbage NO3−-N content was significantly and negatively correlated with the soil Myxococcota, endophytic bacterial community co-occurrence network edge, cabbage soluble sugar and cabbage proline. The GO application generated double-edged sword effects of positively promoting yield but causing risks of NO3−-N accumulation and quality deterioration. However, these adverse effects could be mitigated by the extra nitrification inhibitor application. The potential ecological risks of GO application to the vegetable quality and endophytic community should be considered.

Temporal assessment of N-cycle microbial functions in a tropical agricultural soil using gene co-occurrence networks.

Microbial nitrogen (N) cycling pathways are largely responsible for producing forms of N that are available for plant uptake or lost from the system as gas or leachate. The temporal dynamics of microbial N pathways in tropical agroecosystems are not well defined, even though they are critical to understanding the potential impact of soil conservation strategies. We aimed to 1) characterize temporal changes in functional gene associations across a seasonal gradient, 2) identify keystone genes that play a central role in connecting N cycle functions, and 3) detect gene co-occurrences that remained stable over time. Soil samples (n = 335) were collected from two replicated field trials in Rwanda between September 2020 and March 2021. We found high variability among N-cycle gene relationships and network properties that was driven more by sampling timepoint than by location. Two nitrification gene targets, hydroxylamine oxidoreductase and nitrite oxidoreductase, co-occurred across all timepoints, indicating that they may be ideal year-round targets to limit nitrification in rainfed agricultural soils. We also found that gene keystoneness varied across time, suggesting that management practices to enhance N-cycle functions such as the application of nitrification inhibitors could be adapted to seasonal conditions. Our results mark an important first step in employing gene networks to infer function in soil biogeochemical cycles, using a tropical seasonal gradient as a model system.

Meta-analysis of the effect of nitrification inhibitors on the abundance and community structure of N2O-related functional genes in agricultural soils

Application of nitrification inhibitors (NIs) in agricultural systems is an important strategy to enhance fertilizer nitrogen use efficiency and mitigate soil nitrous oxide (N2O) emissions. Here, we conducted a global meta-analysis of 88 published studies to assess the response of N2O-related functional gene and transcript abundances, and community structure to NIs application. Application of NIs significantly reduced the abundance of ammonia-oxidizing bacteria ammonia monooxygenase (AOB amoA) genes, AOB amoA transcript and nitrite reductase (nirS and nirK) genes. The effectiveness of NIs on reducing the AOB amoA abundance was influenced by N form, soil texture, soil pH and the experimental type (field vs. laboratory). Specifically, NIs were more effective when a mixed inorganic and organic N source was applied to a medium-textured soils. The NIs effectiveness increased with increasing soil pH. The response of AOB amoA abundance to NIs application was not affected by NI type, N rate, soil moisture, soil temperature and soil organic carbon (SOC). The inhibitory effect of NIs on nirS abundance increased with increasing soil temperature. NIs decreased soil nitrifying enzyme activity (NEA) and denitrifying enzyme activity (DEA) by 34.5 % and 27.0 %, respectively, leading to an overall 63.6 % reduction of N2O emissions. Soil NEA correlated positively with the abundance and community structure of AOB amoA but not with AOA amoA. Decrease in DEA with NIs application coincided with the decreasing nirS and nirK abundances. This global-scale assessment demonstrates that the effectiveness of NIs in reducing N2O emissions was attributed to the inhibiting effects on AOB amoA, nirS and nirK genes. Our findings highlight that NIs' inhibition effects on bacterial ammonia-oxidizing community and the encode enzymes in transformation of nitrite to nitric oxide are the main mechanisms for mitigation of N fertilizer-induced N2O emissions.

Impact of Nitrification Inhibitors on Vegetable Production Yield, Nitrogen Fertilizer Use Efficiency and Nitrous Oxide Emission Reduction in China: Meta Analysis

Due to the long-term excessive fertilization in the vegetable system in China, nitrogen use efficiency (NUE) is low, and the environmental problem is serious. Nitrogen fertilizer combined with nitrification inhibitor is an effective strategy to alleviate the loss of active nitrogen and increase vegetable yield. However, systematic research on the above is lacking. Meta-analysis was used to systematically analyze the effects of nitrogen fertilizer combined with nitrification inhibitors[dicyandiamide (DCD), 3,4-dimethylpyrazole phosphate (DMPP), and 2-chloro-6-(trichloromethyl)pyridine (NP)] on the yield, plant nitrogen uptake, nitrogen fertilizer use efficiency, and nitrous oxide emission reduction effects in vegetable production in China. This study further revealed the impacts of different field management measures on their effects. The results showed that the combination of nitrogen fertilizer and nitrification inhibitor could significantly increase vegetable yield (9.2%), plant nitrogen uptake (10.4%), and nitrogen fertilizer use efficiency (11.2%) but reduce nitrous oxide emissions (28.4%). Among the different types of nitrification inhibitors, NP had the highest impact on the yield-increasing effect and the nitrous oxide emission reduction effect, which were 16.1% and 32.0%, respectively, followed by that of DMPP and DCD. Nitrification inhibitors could significantly increase vegetable yield (6.7%-14.7%) and reduce N2O emissions (14.6%-36.8%) in different nitrogen fertilizer rates. In neutral and alkaline vegetable soil, the yield-increasing effect and the reduction effect of nitrous oxide were higher than those in acidic soil. Nitrification inhibitors had significant effects on yield increase and nitrous oxide reduction under the conditions of greenhouse or open-field cultivation, root vegetables, and leafy vegetables. Principal component analysis (PCA) showed that soil total nitrogen content and soil pH were the main factors that promoted the increase in vegetable yields and drove nitrous oxide emissions under the application of nitrification inhibitors. In summary, nitrification inhibitors were an important measure to achieve the goal of improving quality and fertilizer use efficiency, while saving fertilizer and reducing emissions in vegetable production. Farmers should choose suitable types of nitrification inhibitors according to soil and field management measures to maximize their effectiveness.

Changes in soil microbial communities in response to repeated application of nitrification inhibitors

In order to assess the changes in soil physio-chemistry, the abundances and community structures of the N-cycling microorganisms, as well as total bacteria, after repeated application of dicyandiamide (DCD) and 3,4-dimethylpyrazolphosphate (DMPP), samples of soil were obtained from a field experiment where DCD and DMPP had been applied along with fertilizer annually for over 13 years. A randomized complete block design was used that included four treatments: no fertilization (CK), fertilizer application (NPK), NPK + DCD, and NPK + DMPP; each treatment with three replicates. Results showed that repeated chemical fertilizer application led to lower soil pH, significantly higher potential nitrification rates (PNRs) and increased population sizes of ammonia oxidizers compared with the control. However, soil pH was unaffected by the application DMPP or DCD over 13 years. Application of DMPP decreased the PNR and the abundance of ammonia-oxidizing bacteria (AOB) and nirK genes, compared to NPK, but DCD addition exhibited inhibitory effects only on PNR. There were no inhibitor- or fertilizer-induced changes in the abundances of nirS, nosZ and 16S rRNA genes. In addition, the results demonstrated that the community compositions of total bacteria and ammonia oxidizers were not altered by N addition and use of inhibitors at the phylum level. The DCD and DMPP inhibitors, therefore, appear to be effective mitigation technologies targeting specific microorganisms with no long-term adverse impact on the soil ecosystem.

Nitrification inhibitor application at stem elongation stage increases soil nitrogen availability and wheat nitrogen use efficiency under drought stress

ABSTRACT One of the practices which could mitigate the negative effects of drought stress is ammonium nutrition. Nitrification inhibitor (DMPP) can keep ammonium concentrations high in the soil for several weeks. Although there are contradictory reports regarding the priority of NH4 + uptake and its toxicity effects on wheat, it is necessary to understand better how to apply DMPP to increase drought tolerance without any negative effects. The field experiment was conducted using 15N trace technology. The fertilizers treatment included (15NH4)2SO4 and (15NH4)2SO4 with DMPP at four drought stress levels. Available soil mineral nitrogen was measured, as well as yield components and 15N recovery. The results showed that DMPP application at full irrigation and moderate drought stress caused an increase in grain yield of 13% and 10%, respectively. DMPP application at full irrigation, moderate and severe drought stress caused a significant increase in nitrogen use efficiency of 19%, 11%, and 17%, respectively. It seems DMPP application at the stem elongation stage, promoted NH4 + assimilation and transfer to the shoots, which has created relative resistance to drought stress conditions. In conclusion, it is recommended that farmers use DMPP at stem elongation to avoid wheat yield reduction and nitrogen recovery under drought stress.

Effects of combined nitrification inhibitors on soil nitrification, maize yield and nitrogen use efficiency in three agricultural soils

Application of nitrification inhibitors (NIs) with nitrogen (N) fertilizer is one of the most efficient ways to improve nitrogen use efficiency (NUE). To fully understand the efficiency of NIs with N fertilizer on soil nitrification, yield and NUE of maize (Zea mays L.), an outdoor pot experiment with different NIs in three soils with different pH was conducted. Five treatments were established: no fertilizer (Control); ammonium sulfate (AS); ammonium sulfate + 3, 4-dimethyl-pyrazolate phosphate (DMPP) (AD); ammonium sulfate + nitrogen protectant (N-GD) (AN); ammonium sulfate + 3, 4-dimethyl-pyrazolate phosphate + nitrogen protectant (ADN). The results showed that NIs treatments (AD, AN and ADN) significantly reduced soil nitrification in the brown and red soil, especially in AD and ADN, which decreased apparent nitrification rate by 28% - 44% (P < 0.05). All NIs treatments significantly increased yield and NUE of maize in three soils, especially ADN in the cinnamon soil and AD in the red soil were more efficiency, which significantly increased maize yield and apparent nitrogen recovery by 5.07 and 6.81 times, 4.39 and 8.16 times, respectively. No significant difference on maize yield was found in the brown soil, but AN significantly increased apparent nitrogen recovery by 70%. Given that the effect of NIs on both soil nitrification and NUE of maize, DMPP+N-GD was more efficient in the cinnamon soil, while N-GD and DMPP was the most efficiency in the brown and red soil, respectively. In addition, soil pH and soil organic matter play important role in the efficiency of NIs.

Effect of nitrification inhibitor (DMPP) on nitrous oxide emissions from agricultural fields: Automated and manual measurements

Nitrogen fertilisation contributes significantly to the atmospheric increase of nitrous oxide (N2O). Application of nitrification inhibitors (NIs) is a promising strategy to mitigate N2O emissions and improve N-use efficiency in agricultural systems. This study investigated the effect of NI, 3,4-dimethylpyrazol phosphate (DMPP) on N2O mitigation from spring barley and spring oilseed rape. Manual and automatic chamber methodologies were used to capture spatial and temporal variability in N2O emissions. In a second experiment, we study the effect of N fertiliser levels without NI (0 %, 50 %, 100 %, 150 % and 200 % of recommended amount of N fertiliser), as well as 100 % of N with NI on N2O emissions in spring barley. The automated chamber measurements showed dynamics of N2O changes throughout the season, including positive and negative peaks that were unobservable with manual chambers due to low temporal resolution. Although not significant, application of NI tended to reduce N2O emissions. The reduction was on average 16 % in spring barley and 58 % in spring oilseed rape in manual chamber measurements. However, N2O reduction was 108 % in continuous automatic chamber measurements in spring barley. The N2O EFs for the growing season were very low (0.025 % to 0.148 %), with a greater reduction in EF in spring oilseed rape (76 %) than in spring barley (32 %) with NI application. A positive correlation (R = 80 %) was observed between N fertiliser levels and N2O emissions. Crop yield and crop N uptake were not significantly affected by the use of NI. This study highlighted that NI can reduce N2O emissions, but the reduction effects are plot, crop and microclimate specific. Long-term experiments with continuous plot-scale measurements are needed to capture and optimise N2O mitigation effect of NIs across wide variability in soils and microclimates in agroecosystems.

Can nitrogen input mapping from aerial imagery improve nitrous oxide emissions estimates from grazed grassland?

Most nitrogen (N) lost to the environment from grazed grassland is produced as a result of N excreted by livestock, released in the form of nitrous oxide (N2O) emissions, nitrate leaching and ammonia volatilisation. In addition to the N fertiliser applied, excreta deposited by grazing livestock constitute a heterogeneous excess of N, creating spatial hotspots of N losses. This study presents a yearlong N2O emissions map from a typical intensively managed temperate grassland, grazed periodically by a dairy herd. The excreta deposition mapping was undertaken using high-resolution RGB images captured with a remotely piloted aircraft system combined with N2O emissions measurements using closed statics chambers. The annual N2O emissions were estimated to be 3.36 ± 0.30 kg N2O–N ha−1 after a total N applied from fertiliser and excreta of 608 ± 40 kg N ha−1 yr−1. Emissions of N2O were 1.9, 3.6 and 4.4 times lower than that estimated using the default IPCC 2019, 2006 or country-specific emission factors, respectively. The spatial distribution and size of excreta deposits was non-uniform, and in each grazing period, an average of 15.1% of the field was covered by urine patches and 1.0% by dung deposits. Some areas of the field repeatedly received urine deposits, accounting for an estimated total of 2410 kg N ha−1. The method reported in this study can provide better estimates of how management practices can mitigate N2O emissions, to develop more efficient selective approaches to fertiliser application, targeted nitrification inhibitor application and improvements in the current N2O inventory estimation.

Nitrapyrin Addition Mitigated CO2 Emission from a Calcareous Soil Was Closely Associated with Its Effect on Decreasing Cellulolytic Fungal Community Diversity.

Application of nitrification inhibitors (NIs) has been widely used to inhibit nitrification and reduce N2O emissions. However, the impacts of NI addition on soil carbon transformation and carbon-degrading microbial communities have not been well explored. Here, a microcosm experiment was carried out, and four treatments were designed: (i) unfertilized control, (ii) urea alone, (iii) urea plus cattle manure, and (iv) urea plus cattle manure with nitrapyrin. The influence of nitrapyrin on soil CO2 emissions, carbon-degrading extracellular enzyme activities, and the abundance and diversity of the cbhI community was investigated. Compared to the treatment of urea plus cattle manure, nitrapyrin significantly decreased cumulative CO2 emissions by 51.8%. Moreover, cbhI community gene copies and their α-diversities (P < 0.05) were also significantly reduced by nitrapyrin application. A partial least squares path model showed that CO2 emission was positively associated with cbhI community α-diversity but negatively associated with nitrapyrin addition. We conclude that the mitigation of soil CO2 emissions by nitrapyrin can be ascribed to its effects on decreasing of cellulose-degrading gene community diversity. Our findings provide new insights into the side-effects of nitrapyrin on abating CO2 emission.

Effects of Nitrification Inhibitors on Nitrogen Dynamics and Ammonia Oxidizers in Three Black Agricultural Soils

The application of nitrification inhibitors (NIs) based on ammonium (NH4+) is considered to be an efficient way to reduce nitrogen (N) loss by delaying the nitrification process through influencing ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB). However, the inhibition mechanisms of NIs on AOA and AOB in different soils remain unclear. Hence, we explored the two commonly used NIs (3, 4-dimethylepyrazole phosphate (DMPP) and dicyandiamide (DCD) and their combination (DMPP + DCD) on the soil nitrification and abundance of ammonia oxidizers (AOA and AOB) in three black soils (HLJ, NA, and DA) with different physicochemical properties using a 120-day incubation experiment. The results demonstrated that NIs significantly increased NH4+-N concentrations and decreased NO3−-N concentrations in all three tested soils. There was no significant difference in inhibiting nitrification in HLJ among all NI treatments, while DCD was more efficient in NA, DMPP + DCD had better efficiency in DA. The potential nitrification rate (PNR) was greatly decreased by NIs addition, and PNR was significantly positively correlated with AOB (p &lt; 0.05). AOA was dominant in the acid soil. All NI treatments significantly inhibited soil nitrification through inhibiting the growth of AOB in the two soils with higher pH. The abundance of AOA and AOB was significantly correlated with different soil types (positively correlated with soil pH, and negatively correlated with organic matter). Moreover, soil pH and soil organic matter were considered to be the most important factors influencing the inhibition efficiency of NIs and the abundance of AOA and AOB. The application of the NIs combination (DMPP + DCD) was considered to be the most cost-effective way to inhibit soil nitrification in soil with higher pH and lower SOM, which provides a theoretical basis for a field experiment.

A global synthesis of soil denitrification: Driving factors and mitigation strategies

Dinitrogen (N2) and nitrous oxide (N2O) produced via denitrification may represent major nitrogen (N) loss in terrestrial ecosystems. A global assessment of soil denitrification rate, N2O/(N2O+N2) ratio, and their driving factors and mitigation strategies is lacking. We conducted a global synthesis using 225 studies (3367 observations) to fill this knowledge gap. We found that daily N loss through soil denitrification varied with ecosystems and averaged 0.25 kg N ha−1. The average emission factor of denitrification (EFD) was 4.8%. The average N2O/(N2O+N2) ratio from soil denitrification was 0.33. Soil denitrification rate was positively related to soil water-filled pore space (WFPS) (p < 0.01), nitrate (NO3-) content (p < 0.05) and soil temperature (p < 0.01), and decreased with higher soil oxygen content (p < 0.01). N2 emissions increased with latitude (p < 0.05), WFPS (p < 0.01) and soil mineral N (p < 0.05) but decreased with soil oxygen content (p < 0.05). The N2O/(N2O+N2) ratio increased with soil oxygen content (p < 0.01) but decreased with organic carbon (C) (p < 0.05), C/N ratio (p < 0.01), soil pH (p < 0.05) and WFPS (p < 0.01). We also found that optimizing N application rates, using ammonium-based fertilizers compared to nitrate-based fertilizers, biochar amendment, and application of nitrification inhibitors could effectively reduce soil denitrification rate and associated N2 emissions. These findings highlight that N loss via soil denitrification and N2 emissions cannot be neglected, and that mitigation strategies should be adopted to reduce N loss and improve N use efficiency. Our study presents a comprehensive data synthesis for large-scale estimations of denitrification and the refinement of relevant parameters used in the submodels of denitrification in process-based models.

Changes in Ammonia Oxidizers, Denitrifiers and Non-Targeted Microbial Abundance and Community in Response to Repeated Application of Nitrification Inhibitors in Agricultural Soil

Changes in Ammonia Oxidizers, Denitrifiers and Non-Targeted Microbial Abundance and Community in Response to Repeated Application of Nitrification Inhibitors in Agricultural Soil

Dimethylpyrazole-based nitrification inhibitors have a dual role in N2O emissions mitigation in forage systems under Atlantic climate conditions

Nitrogen fertilization is the most important factor increasing nitrous oxide (N2O) emissions from agriculture, which is a powerful greenhouse gas. These emissions are mainly produced by the soil microbial processes of nitrification and denitrification, and the application of nitrification inhibitors (NIs) together with an ammonium-based fertilizer has been proved as an efficient way to decrease them. In this work the NIs dimethylpyrazole phosphate (DMPP) and dimethylpyrazole succinic acid (DMPSA) were evaluated in a temperate grassland under environmental changing field conditions in terms of their efficiency reducing N2O emissions and their effect on the amount of nitrifying and denitrifying bacterial populations responsible of these emissions. The stimulation of nitrifying bacteria induced by the application of ammonium sulphate as fertilizer was efficiently avoided by the application of both DMPP and DMPSA whatever the soil water content. The denitrifying bacteria population capable of reducing N2O up to N2 was also enhanced by both NIs provided that sufficiently high soil water conditions and low nitrate content were occurring. Therefore, both NIs showed the capacity to promote the denitrification process up to N2 as a mechanism to mitigate N2O emissions. DMPSA proved to be a promising NI, since it showed a more significant effect than DMPP in decreasing N2O emissions and increasing ryegrass yield.

Identifying agronomic practices with higher yield and lower global warming potential in rice paddies: a global meta-analysis

Rice agriculture faces the dual challenge of increasing grain production while reducing global warming potential (GWP). Yield-scaled GWP, a commonly employed indicator, is not sufficient to identify smart agronomic practices that can address this dual challenge. Thus, practices that can increase yield while simultaneously reducing GWP in rice paddies have not yet been clearly defined. In this study, we synthesised independent experiments by meta-analyses to identify agronomic management practices with higher rice yield and lower GWP. The results showed that the application of nitrification inhibitors (NI) and biochar significantly increased rice yield by an average of 9.5% and 9.1%, and simultaneously reduced GWP by 24% and 14%, respectively. Overall, controlled-release nitrogen (N) fertilisers did not affect GWP despite increasing rice yield (+9.2%). In contrast, conventional N application enhanced both rice yield (+44%) and GWP (+27%). No-tillage reduced GWP (˗23%) but did not significantly affect rice yield. Non-continuous flooding in rice paddies significantly reduced GWP (˗48%) but also reduced the yield (˗4.2%). The rice yield and GWP outcomes were similar for rice-animal co-culture and rice monoculture systems. In conclusion, both NI and biochar application are promising practices for increasing yield while simultaneously reducing GWP in rice paddies. In addition, we suggest that individual agronomic practices should be combined to increase rice yield while mitigating climate warming.

Effects of Nitrification Inhibitors on Soil Nitrification and Ammonia Volatilization in Three Soils with Different pH

The application of nitrification inhibitors (NIs) is considered to be an efficient way to delay nitrification, but the effect of NIs combinations on soil nitrification and ammonia (NH3) volatilization are not clear in soils with different pH values. In this study, we explored the effect of nitrapyrin (CP) and its combinations with 3, 4-dimethylepyrazole phosphate (DMPP), dicyandiamide (DCD) on the transformation of nitrogen, potential nitrification rate (PNR), and ammonia (NH3) volatilization in a 120-day incubation experiment with three different pH values of black soil. Treatments included no fertilizer (Control), ammonium sulfate (AS), AS+CP (CP), AS+CP+DMPP (CP+DMPP), and AS+CP+DCD (CP+DCD). The application of NIs significantly decreased NO3−-N contents and potential nitrification rate (p &lt; 0.05), while significantly increased NH4+-N contents (p &lt; 0.05), especially CP+DCD and CP+DMPP were the most effective in the neutral and alkaline soils, respectively. In the acid soil, CP significantly increased total NH3 volatilization by 31%, while CP+DCD significantly reduced by 28% compared with AS. However, no significant difference was found in NH3 volatilization with and without NIs treatments (p &gt; 0.05) in the neutral and alkaline soils. In conclusion, the combined nitrification inhibitors had the better efficiency in all three tested soils. CP+DCD and CP+DMPP are the most effective in inhibiting soil nitrification in the clay soils with higher pH value and lower organic matter, while CP+DCD had the potential in mitigating environment pollution by reducing N loss of NH3 volatilization in the loam soil with lower pH value and higher organic matter. It provided a theoretical basis for the application of high efficiency fertilizer in different soils. Further studies under field conditions are required to assess the effects of these nitrification inhibitors.